Dave Roeser inspects rotating beds of lettuce seedlings. “Consumers can get fresh produce — grown without pesticides — within days of being harvested all year long,” he says. “It’s much fresher than produce shipped from California.” (File photo: Bill Klotz)

What can you do with an old warehouse that nobody wants? How about turning it into a self-contained and sustainable indoor farm, and grow produce year-round for the surrounding community?

That is what Dave Roeser and his wife, DJ, did at two locations — one in Maplewood and one in the Midway area of St. Paul — with plans to build more.

In 2010 they established Garden Fresh Farms, indoor hydroponic farms that grow lettuce, “microgreens” and herbs. Using patent-pending technology developed by their son Bryan, a biosystems manager, they grow the produce in a vertical space using specially designed growing surfaces that turn slowly on cylinders around the light source. Not only do they use less land, but they also use 90 percent less water than field irrigation. This method can yield 100 acres of produce in a one-acre space.

For fertilizer, they farm fish. It’s a complete cycle — nutrient-rich water is pumped from the fish tank to the plants and sent back again. No water goes down the drain.

The produce is sold locally at stores including Whole Foods, community co-ops, through Community Supported Agriculture subscriptions, and it is used in restaurants and corporate dining.

“Our St. Paul location is within two miles of distributors,” said Dave Roeser, president. “Consumers can get fresh produce — grown without pesticides — within days of being harvested all year long. It’s much fresher than produce shipped from California.”

To grow their business, the Roesers are selling 5,000-square-foot “farm units” at their large St. Paul location to investors. Their management company, GFF Management LLC, runs the farms. The first phase is complete and harvesting daily; phase two is scheduled to be complete by mid-March.

The farm units yield 1,200 heads of lettuce and 40 pounds of basil a day for gross revenue of $350,000 per year. Each farm creates five jobs, with up to 25 jobs to be created in St. Paul.

Roeser’s goal is to build 10 farms in 10 cities over the next two or three years. They have had inquiries from investors in other cities, as well as other countries, including Russia and Japan.